Color takes on different appearances under different viewing conditions in such as the illumination white point, the illumination brightness, the ambient light level and the like. While the von Kries chromatic adaptation model in the known art is often adopted when executing chromatic adaptation transform taking into consideration the difference between the white points, the CIECAM02 may be adopted as a color appearance model if further details in the difference between the viewing conditions, including the difference in the luminance and the difference in the ambient light level, must be factored in. Since visual perception is not always completely adapted to the illumination provided in a given viewing condition, chromatic adaptation transform may be executed based upon an adaptation factor D (0.0≦D≦1.0) indicating the degree to which visual perception is adapted to the white point.
The adaptation factor D is determined in conformance to the viewing condition. For instance, in the color appearance model CIECAM 97s or CIECAM02 defined by the CIE, a value determined in correspondence to the illumination brightness or the ambient light level (whether the surrounding environment is light or dark) is utilized (see patent reference 1). Patent reference 2 proposes a method whereby the adaptation factor is altered based upon the correlated color temperature of the illumination.
Patent reference 1: Japanese Patent Publication No. 3634633.
Patent reference 2: Japanese Laid Open Patent Publication No. H11-055688